Method and system for estimating RMS of AC voltage

Abstract

A method of estimating a root mean square (RMS) of an alternating current (AC) voltage is provided. The system includes a rectifier configured to rectify the AC voltage and a controller configured to derive a delayed AC voltage by delaying the rectified AC voltage by a preset delay time. The controller is configured to estimate a root mean square (RMS) of the AC voltage based on the rectified AC voltage and the delayed AC voltage.

What is claimed is: 
     
       1. A method of estimating a root mean square (RMS) of an alternating current (AC) voltage for a charging device configured to charge a high-voltage battery of a vehicle, the method comprising:
 rectifying, by a rectifier, the AC voltage; 
 deriving, by a processor, a delayed AC voltage by delaying the rectified AC voltage; 
 estimating, by the processor, the RMS of the AC voltage using the rectified AC voltage and the delayed AC voltage; and 
 adjusting, by the processor, the charging device which uses the AC voltage to charge the high-voltage battery of the vehicle based on the estimated RMS of the AC voltage, 
 wherein the deriving the delayed AC voltage includes:
 deriving, by the processor, a frequency of the rectified AC voltage; 
 deriving, by the processor, a delay time based on the frequency; and 
 deriving, by the processor, the delayed AC voltage by delaying the rectified AC voltage by the delay time, 
 
 wherein the deriving the delay time includes deriving, by the processor, the delay time using an equation indicated below:
     T   d =1/(4* F   AC ), 
 
 wherein T d  is the delay time, and F AC  is the frequency of the rectified AC voltage, and 
 wherein the estimating the RMS of the AC voltage includes compensating, by the processor, the delay time attributed to a response delay. 
 
     
     
       2. The method according to  claim 1 , further comprising:
 scaling, by the processor, the rectified AC voltage a number of times equal to a predetermined constant. 
 
     
     
       3. The method according to  claim 1 , wherein the estimating the RMS of the AC voltage further includes:
 deriving, by the processor, the square of the delayed AC voltage and the square of the rectified AC voltage; 
 multiplying, by the processor, the square of the delayed AC voltage by the square of the rectified AC voltage; and 
 estimating, by the processor, the RMS of the AC voltage by multiplying a predetermined transform constant by the multiplied result. 
 
     
     
       4. The method according to  claim 3 , wherein the transform constant is √{square root over (2)}. 
     
     
       5. A system for estimating a root mean square (RMS) of an alternating current (AC) voltage for a charging device configured to charge a high-voltage battery of a vehicle, the system comprising:
 an AC voltage supply configured to supply the AC voltage; 
 a rectifier configured to rectify the AC voltage; and 
 a processor configured to derive a delayed AC voltage by delaying the rectified AC voltage, to estimate the RMS of the AC voltage using the rectified AC voltage and the delayed AC voltage, and to adjust the charging device which uses the AC voltage to charge the high-voltage battery of the vehicle based on the estimated RMS of the AC voltage, 
 wherein the processor is further configured to derive a frequency of the rectified AC voltage, a delay time based on the frequency, and the delayed AC voltage by delaying the rectified AC voltage by the delay time, 
 wherein the processor is further configured to derive the delay time using an equation indicated below:
     T   d =1/(4* F   AC ), 
 
 wherein T d  is the delay time, and F AC  is the frequency of the rectified AC voltage, and 
 wherein the processor is further configured to estimate the RMS of the AC voltage by compensating the delay time attributed to a response delay. 
 
     
     
       6. The system according to  claim 5 , further comprising a transform having a constant of √{square root over (2)}.